Work holding fixture and power means for operating the same



J1me 1954 A. H. Pr-zAsou 2,681,581

WORK HOLDING FIXTURE AND POWER D MEANS FOR OPERATING THE SAME Flled May 10, 1950 2 Sheets-Sheet 1 W i ,4 n

5 J4 a 60 4a a? 49 a f/ 62 0'9 4 7 J i\\ A 6'? J I f a 65 4; INVENTOR.

A. H. PEARSON WORK HOLDING FIXTURE AND POWER MEANS FOR OPERATING THE SAME June 22, 1954 2 Sheets-Sheet 2 Filed May 10, 1950 INVENTOR. 4/00 ea/290x? BY ATTOAAfiF Patented June 22, 1954 WORK HOLDING FIXTURE AND POWER MEAN S FOR'OPERATING THE SAME Alan H.. Pearson, Detroit, Mich., assignor to -Pearson,Inc., Detroit, Mich., a corporation of Michigan Ap'plicationMaylO, 1950, Serial No. 161,101

' 4 Claims.

This invention relates generally to work holding fixtures and refers more particularly to. improvements in fixtures of the type awhich'automatically look upon. engaging .the:work. ton-be clamped.

Fixtures of. the above: general type are used extensively in production,.becauseof the rapidity with which they maybe operatedgand-because of the rigidity with which they retain the work inposition during machining or other operations. One objection to such fixtures-is that they must be hand operated, and considerableltime may be lost in productionbecause of the necessity for the operatorto free at least" one. hand formanipulation of the fixture.

With the abovein view, itis an object'of this invention to provide a work clamping fixture with means for automatically.operatingthe fixture to both its clamping and-released pos'itionsby mere- 1y touching a control which may be located in av position for convenient operation by one foot of the operator. However,xeven in instances where itcis desired to operate the control'bya hand of the operator, considerable time issaved'over a long period of .use,.since it is only necessary for the operator to touch the control. Also operator fatigue is reduced to: a minimum, and personal efficiency materially increased.

It is another feature of this invention to automatically operate the work clamping fixture with a power unit which is compact in construction and may be readily adaptedto orthodox rwork clamping fixtures in a matter of minutes without. materially altering the fixture.

The foregoing as wellas other objects will be made more apparent as this description proceeds, especially when considered in connectionwith the accompanying drawings, wherein:

Figure 1 is a perspective view of a typical work clamping fixture having a. power unit embodying the features of this "inventionattached thereto;

Figure 2 is a sectional view taken substantially on the line 2-2 of Figure 1;

Figure 3 is a cross sectional viewtaken'on the line 3-3 of Figure 2;

Figure 4 is a cross sectionalview taken on the line 4-4 of Figure 3; and

Figure 5 is a sectional view showing; a slightly modified form of. power unit.

The power units illustratedin Figures 1.to 5 inclusive are shown-for theepurpose of illustrationas installed on a type of .work holding fixture which has enjoyed;practicallyauniversal acceptancesby the trade for clamping work pieces in position during machining or other. work .per-

2 forming operations. Such fixtures ordinarily embody a quick acting lock for securely holding the work pieces against accidental: movement during the work performing operation, and this lock is. usually manipulated by a hand. operated lever on the fixture. .In accordance withxthe present invention, fixtures of the above general type may bequickly converted to automatic operation by merely removing the handle assembly,

, and attaching the power unit shown in Figures 1 tot inclusiveof the drawings. The power unit featured in Figure 5 of the drawings incorporates the locking means as a part of itsassembly, and has many diversified uses.

Referring first to the embodiment of the invention shown in Figures 1 to 4 inclusive, itwill be noted that the reference numeral Ill in Figure 1 designates a typical work holding fixture, and the numeral II indicates a power unit for the fixture. The fixture selected herein for the purpose of illustration comprises abase I2. and a clamping plate I3 spaced vertically aboveithe base I2. Thezbase I2 has ;a worknsupporting surface I4 and-a pair of laterally spaced vertical housings I5 extending upwardly from: the base at one side of the surface I4. The clamping plate i3 has a pair of vertical shafts I6- respectively secured at the upper ends to the plate I3 by studs I1 and spaced laterally from each other in a manner such. as to telescopically engage within the housings I5.

A driven shaft I8 extends perpendicular to the shafts I6 and is journalled in suitable bores formed in the vertical housings I5. The opposite end portions of the driven shaft respectively intersect the vertical path of travel of the shafts I B and are formed with an annular series of teeth I9. The teeth I9, in effect, formpinions on the shaft I8 and respectively meshwith rack teeth 283' formed on the adjacent sidesof the vertical shafts I6. The arrangement is such that rotation of the driven shaft I8 in a forward direction, or in the direction of the arrow 2 I, lowersthe'plate I3 into clamping position and rotation of the driven shaft I8 in the opposite-or-rearward direction'raises the: clampingplate I 3 to its released position.

The clamping plate I3 is securely held in its clamping position by means of a locking'device 22. The locking device 22 has a ring 23 concentrically positioned with respect to the driven shaft and removably secured to one side of the fixture I!) by studs 25. It will be noted from Figure 3 of the drawings that the adjacent end. of the drivenshaft' It has a reduced portion 25 which 3 &

for a cam 26. The cam 26 is keyed to the driven shaft for rotation as a unit with the latter, and the periphery of the cam 26 is fashioned with three flats 21 spaced equal distances from each other circumferentially of the cam. It will be noted from Figure 4 of the drawings that the flats 2? cooperate with the inner surface of the ring 23 to form wedge-shaped spaces 28 and also provide shoulders 22%. Suitable rollers 38 are re spectively supported in the spaces 28 and these rollers are adapted to move into wedging engagement with the flats 27 and the inner surface of the ring 23 to effectively lock the clamping plate [3 in its clamping position. In other words when the rollers 36 are in their wedging position, rotation of the driven shaft is by the load in the reverse direction is prevented.

The rollers 30 are released from their wedging position to enable moving the clamping plate It to its inoperative position by a hub 3| supported at the front side of the ring 23 for rotation about the axis of the driven shaft l3. In accordance with conventional practice the hub is formed With three fingers 32 which project into the ring 23' and assume positions at the outer side of the cam 26 between the rollers 38. The arrangement is such that rotation of the hub 3! in a rearward direction engage the fingers with the rollers and shifts the latter out of Wedging position. Thus the locking device 22 is released and the plate 13 may be returned to its released or inoperative position. On the other hand, rotation of the hub 3| in a forward direction imparts a thrust on the cam 26 tending to rotate the latter in a corresponding direction. As a result the rolls are released from their wedging. positions, and the driven shaft 18 i rotated in the direction of the arrow 2| to move the plate I3 to its clamping position.

In conventional locking fixtures of the above general type, the hub 3! is attached to a hand operated lever. In the present instance, however,

the hub 3! forms apart ofthe power unit H,

and is operated by the latter.

The power unit I 5 comprises a housing 35 which may be in the form of a casting, and is fashioned with a casing 36 shown in Figure 3 of the drawings as aligned with the driven shaft :8. The

inner end of the casing 36 has a cup-shaped portion 3? designed to receive the ring 23' of the locking device and is secured to the fixture m by the studs 24. The outer end of the casing is closed by a cap 33, and a fluid-tight joint is provided by a seal 39.

A drive shaft 49 is journalled within the casing 36 in axial alignment with the driven shaft l3, and the inner end of the shaft 4!! is secured to a part ll by a key 42. The part 4! is rotatably supported in the casing 36, and is secured or formed integral with the hub 31 for operating the latter. The arrangement is such that the locking device 22 serves as a unidirectional driving connection between the driving shaft 4e and the driven shaft 18. A suitable packing 3 is provided around the shaft 49 at the inner side of the part 4!, and the seal as also has a part 44 which engages the outer end of the shaft 40 to prevent escape of fluid along the shaft from the interior of the casing 36.

The driving shaft 43 is rotated in opposite directions by a fluid motor, which is adapted for operation by either air or liquid under pressure. The fluid motor comprises a cylinder 45 and a double-acting piston slidably supported within the cylinder. The cylinder 45 is formed on the housing 35 and extends at right angles to the casing 36. The ends of the cylinder 45 project laterally beyond opposite sides of the casing 36 at the outer end of the latter and the interior of the cylinder communicates with the interior of the casing 36 to enable projecting the shaft 40 across the cylinder.

One end 4'! of the cylinder is reduced in diameter, and is closed by a cap 48 which is removably secured to the housing 35 by studs 55. The opposite or relatively large diameter end 56 of the cylinder 45 accommodates the piston 46, and is closed by a cap 5|, which is removably secured to the housing by studs 52.

The housing 35 is fashioned with ports 53 and 54 respectively positioned to communicate with the interior of the cylinder adjacent opposite ends of the latter. As shown particularly in Figure 2 of the drawings, the ports 53 and 54 are alternatively connected by a four-way valve 55 to a fluid supply line 56 and to an exhaust line 51. The valve 55 may be operated by any suitable means (not shown) located at any selected point with respect to the fixture. As an example the valve 55 may be operated by a solenoid operated switch having a control positioned for convenient manipulation by one foot of the operator.

The piston 46 is of the balanced type, or in other words, is of a design which presents equal areas at opposite sides to the action of fluid under pressure. In detail the piston has a centrally apertured disc 58 clamped between a pair of heads 59 and 6B. The head Bil extends through the central opening in the disc and is formed with an axially extending internally threaded bore 62. The head 59 has a stud 63 which threadably engages in the bore 62. A pair of opposed generally cup-shaped sealing elements 65 are provided on the piston to prevent escape of fluid under pressure past the piston when the latter is shifted in either direction in the cylinder.

Referring again to Figure 2 of the drawings, it will be noted that the head '60 has an axially projecting part 66 in the form of a shaft. The part 66 slides in the reduced portion 41 of the cylinder 45, and the top surface of the part 'is fashioned with a lurality of rack' teeth 61. The teeth 6? are arranged in mesh with a pinion 68 formed integral with the adjacent portion of the shaft 4?). 'It will also be noted that the part 66 has an axially extending passage as, which extends from the free end of the part to the head 6t of the piston and opens into the cylinder at the adjacent side of the piston. The purpose of the passage is to facilitate the flow of fluid under pressure between the port 54 and the adjacent side of the piston 46.

I Operation Assuming that the valve 55 is in a position wherein the fluid pressure supply line 55 is connected to the port 53 and the exhaust line 51 is connected to'the port 54, it will be noted that the piston 46 is moved from the position shown in Figure 2 toward the port 54. As a result the shaft 4!} is rotated in the direction of the arrow 10 in Figure 2, and the hub 3| in Figure 3 is rotated in a corresponding direction. Thus the rollers 39 in the locking'device 22 are released, and the driven shaft I8 is rotated in the direction of the arrow H in Figure 3 to move the plate l3downv wardly to its clamping position.

As soon as the plate i3 reaches its clamping position, rotation of the driven shaft I8 ceases,

and the rollers positively lock the shaft against reverse rotation by the reaction of the load on the clamp. Thus if for any reason thepressure of the fluid should dropor fail completely, the fixture is retained in its clamping position by the locking device 22, and danger of harming the operator, machine or tools is avoided.

When it is desired to release the clamp, the four-way valve 55 is operated to connect the port 54 to the fluid pressure supply line 56 and to connect the port 53 to the exhaust line '51. As a result the piston 46 is moved in a direction toward the port 53, and the drive shaft 4!! is rotated by the rack part 65in therever-se direction. Thus the hub 3| releases the rollers from Wedging contact with the fixed ring 23 and permits reverse rotation of the driven shaft l8 to lift the clamping plate 13 'toits inoperative position.

In accordance with this invention, the flow of fluid under pressure through the ports 53 and 54 may be independently varied by suitable metering pins H and 12. Thus the speed of operation of the clamp in either direction may be varied to suit different conditions, and the torque may be controlled, if desired.

The embodiment of the invention shown in Figure 5 of the drawings differs essentially from the above construction in that the locking device 22 is incorporated within the power unit II. More particularly it will be noted that the casing 3 6 of the housing is fashioned to accommodate the locking device 22. The locking device 22 is essentially the same as the locking device 22, and corresponding parts are indicated by the same reference numerals. It may be pointed out that the ring 23 is secured against rotation relative to the casing 36 by a pin 76, and the hub 3! is secured against rotation relative to the shaft 40 by a pin H. The cam 26 of the locking device is keyed to a driven shaft 13 which projects through a central opening formed in a closure cap 19 for the inner end of the casing. The shaft I8 may be coupled to the driven shaft l8 of the fixture ID, or may be coupled to any suitable device. In other words the embodiment of the invention shown in Figure 5 may be used for operating devices other than work holding clamps. In any case the operation of the power unit shown in Figure 5 is generally the same as the operation of the power unit shown in Figures 1 to 4 inclusive.

What I claim as my invention is:

1. A power unit for a work holding fixture having a clamping member supported for movement into and out of clamping position, said power unit comprising a fluid motor for moving the clamping member into and out of clamping position, said fluid motor having a cylinder, said cylinder having a portion at one end of reduced diameter, a double-acting piston slidably supported in the portion of said cylinder of greater diameter, a port in said cylinder adjacent one end thereof and a second port in said cylinder adjacent the opposite end, means for alternately supplying fluid under pressure to and exhausting the same from said ports to move said piston in opposite directions in said cylinder, a part slidably supported in the reduced portion of said cylinder and extending axially of the latter, said part being secured to the adjacent side of said piston for operation by the latter, a passage for fluid extending axially through said part and connecting the reduced portion of said cylinder to the relatively large diameter portion thereof at the side of said piston adjacent said reduced portion, thereby to facilitate the flow of fluid under pressure between the'relatively large diameter portion of said cylinder at the aforesaid side of said piston and the adjacent ort, and means for operatively connectingsaidpart to the clamping member for actuating the latter.

2. A power unit fora work holding fixture having a clamping member supported for movement .into and out of clamping position, said power unit comprising a housing and a fluid motor in said housing for moving the clamping member into and out of clamping position, said fluid-motor having a cylinder, said cylinder having a portionat one endof reduced diameter, a double-acting piston slidably supported in the portion ofsaid cylinder of greater diameter, port in said cylinder adjacent one end thereof and a second port in said cylinder adjacent the opposite end, meansfor alternately supplying fluid under pressure to and exhausting the same from said ports to move said piston in opposite directions in said cylinder, a drive shaft sup ported for rotation by said housing, a rack part slidably supported in the reduced portion of said cylinder and extending axially of the latter, said rack part beieng secured to the adjacent side of said piston for operation by the latter, a pinion within said cylinder secured to said drive shaft and meshing with said rack part for rotating said drive shaft in opposite directions upon movement of said piston in opposite directions, a driven shaft also supported for rotation in substantial alignment with said drive shaft, a unidirectional driving connection between said shafts including releasable means for locking said driven shaft against rotation in one direction, means operated by said drive shaft upon rotation thereof in said one direction to release said locking means and to impart rotation to said driven shaft in said one direction, and means for operatively connecting said driven shaft to the clamping member.

3. The structure set forth in claim 2 wherein said rack part has an axially extending passage therein connecting the reduced portion of said cylinder to the relatively large diameter portion thereof at the side of said piston adjacent said reduced portion, thereby to facilitate the flow of fluid under pressure between the relatively large diameter portion of said cylinder at the aforesaid side of said piston and the adjacent port.

4. A power unit for a work holding fixture having a clamping member supported for movement into and out of clamping position, said power unit comprising a housing and a fluid motor in said housing for moving the clamping member into and out of clamping position, said fluid motor having a cylinder, said cylinder having a portion at one end of reduced diameter, a double-acting piston slidably supported in the portion of said cylinder of greater diameter, a port in said cylinder adjacent one end thereof and a second port in said cylinder adjacent the opposite end, means for alternately supplying fluid under pressure to and exhausting the same from said ports to move said piston in opposite directions in said cylinder, a drive shaft supported for rotation by said housing, a rack part slidably supported in the reduced portion of said cylinder and extending axially of the latter, said rack part being secured to the adjacent side of said piston for operation by the latter, a passage for fluid extending axially through said rack part and connecting the reduced portion of said cylinder to the relatively large diameter portion thereof at the side of said piston adjacent said reduced portion, thereby to facilitate the flow of fluid under pressure between the relatively large diameter portion of said cylinder at the aforesaid side of said piston and the adjacent port, a pinion within said cylinder secured to said drive shaft and meshing with said rack part for rotating said drive shaft in opposite directions upon movement of said piston in opposite directions, and means for operatively connecting said drive shaft to said clamping member.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 563,304 Ongley July 7, 1896 1,095,593 Pike et a1. May 5, 1914 1,230,150 Geraghty June 19, 1917 1,582,966 Brinker et al May 4, 1926 Number 1,808,431

Number Name Date Osborne June 2, 1931 Ferris Sept. 15, 1931 Ewing June 28, 1932 Swartz Oct. 18, 1932 Swartz Nov. 19, 1935 Siewek Jan. 3, 1939 Van Sittert Dec. 10, 1940 Curtis Aug. 31, 1943 Boyd July 23, 1946 Spraragen Sept. 27, 1948 Lee Nov. 9, 1948 Young July 26, 1949 FOREIGN PATENTS Country Date Germany Apr. 13, 1933 Great Britain Mar. 5, 1936 Germany June 12, 1937 

